This is an old problem, and I never figured out how to solve it. Everytime I give some beveled geometry to a curve, the radius of that geometry is smaller in the corners or othe angles. Anybody knows why this happens, and how to make the radius along the curve be the same?

That central loop, when you use the Shear tool, becomes an oblong shape, it stretches the circle to accommodate being used on 2 axis (x and z). The circles on the ends of the pipe only use 1 axis each. I hope that makes sense.

It’s because your curve is 3D. Set it to 2D and you wont have this problem.
If you absolutely need it 3D, you can play with Alt+S on the corner point to change the diameter, but it won’t be fully accurate. I know i fixed it in some way but i don’t remember how